Spontaneous activity of autonomic functions in coma due to drug overdose

Spontaneous heart rate, respiration rate and electrodermal activity were studied in 32 patients with different grades of severe poisoning by ingestion of various drugs. The degree of their behavioural impairment was determined with the Munich Coma Scale (MCS) which measures stimulus evoked somatomotor responses. There was a significant reduction of spontaneous variations of heart rate and respiration rate with increasing severity of coma. Spontaneous electrodermal fluctuations were present only at the least severe grades of impairment. Thus, cardiorespiratory and electrodermal activity can provide significant information on the level of behavioural impairment in severe poisoning.